ANN ARBOR -- Rotate. If there was a theme over the weekend along Tim Drevno and Greg Frey's offensive line, it was exactly that. As the Wolverines begin to work through spring practice over the next three weeks in Ann Arbor, figuring out a firm starting point when it comes to the offensive line has to be at the top of the priority list. Michigan loses three senior starters from a 2016 group that had its way with lesser opponents but struggled in critical moments against elite competition and was ultimately the biggest reason why the club dropped three of its final four games after starting the year 9-0. It's start-over time up front. And right now, Drevno and Frey are just trying to find the best five -- no matter what that combination is. "We'll see who the best five guys are," Drevno said, simply. Michigan knows what it has in senior Mason Cole, a player who has started every game he's played as a Wolverine, and Ben Bredeson -- a sophomore who emerged as a starting guard last season as a true freshman. Cole started all 13 games at center a year ago, but was working all over the place on day one -- he was back out at left tackle (the spot he started his first two years on campus), he was inside. He worked with a variety of different players in different combinations. Cole says that's all fine by him. He'll play anywhere Michigan needs him to. Drevno and company see Cole as an interior lineman in the NFL. That's where his future lies. But the Florida native is open to moving around if he has to. If he does move, one of Michigan's options to fill the void at center comes in the form of its highest-rated offensive line prospect from the 2017 class: Former IMG Academy prospect Cesar Ruiz, the top-rated center recruit in America. Ruiz, like Cole, believes his future is as an interior lineman. But the 6-foot-4, 336-pounder also wants to get on the field as soon as possible. Cole knows what that feels like. "He's really athletic and really football intelligent," Cole says of Ruiz. "He's really intelligent, really athletic. He's going to be a good player. ... I think being really football intelligent is important if you're going to play center, but I think Cesar could play any position. "Body type doesn't matter as much at this level. He could go out and play tackle if he wanted to, play guard if he wanted to. We're going to see how it works." Another player to watch this spring is sophomore Michael Onwenu, a hulking offensive guard prospect from Detroit Cass Tech who played at (at least) 375 pounds last season during his true freshman year. Onwenu has dropped some weight on his 6-foot-3 frame -- but, ultimately, he'll always be huge. Michigan was blown away by Onwenu's raw ability early last year -- especially during fall camp -- and tinkered with the idea of making him a two-way player. Jim Harbaugh and company eventually stuck with the offensive line for Onwenu, but still believe he can serve a role in spot duty as a giant interior tackle in short yardage situations. Either way, Michigan has a guard spot open if Onwenu wants to take it. Now, it's up to him. "I think Mike just has to realize how good he can be," former Michigan guard Kyle Kalis says. "Last year at some practices, he'd be moving Ryan (Glasgow) back and Ryan was one of the best guys we had. Or moving (Bryan) Mone back and Mone is one of the best guys we had. "And he didn't even realize he was going good at the time. Then we're all watching it on film going 'I wish I could do that.' It's so natural for him. Once he figures it all out -- physically and mentally, puts it together -- once the puzzle starts (coming together) he's going to be crazy (good)." Cole and Bredeson are as close to sure things -- in terms of starters -- as Michigan has right now. Both can also move around to different spots if need be. The rest of the crew? Onwenu, Ruiz, Patrick Kugler, Nolan Ulizio, Juwann Bushell-Beatty, Jon Runyan, Stephen Spanellis, JaRaymond Hall and soon-to-be incoming freshmen Chuck Filiaga, Joel Honigford and Andrew Steuber -- they're going to continue rotating through the line until something starts to click. The team still doesn't know if it'll have Grant Newsome back in the fold next year either. Michigan probably won't have a final five set in stone when spring ball ends. But it'll soon find out who it can count on, and who it can't. "We're back and forth," Cole says. "We're trying to find the best five and the best rotation possible. Wherever the pieces of the puzzle fit."